In the field of this invention, it is known for devices to communicate across networks by way of protocols, the protocols acting as a set of rules governing how information, data, etc. is to be sent and/or received. The Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite has become the de facto standard for computer communications in today's networks. The TCP/IP protocol suite is so named for two of its most important protocols: Transmission Control Protocol (TCP) and Internet Protocol (IP). Another name for it is the Internet Protocol Suite, which is the phrase used in official Internet standards documents.
As will be appreciated by a skilled artisan, in wireless systems, for example a Universal Mobile Telecommunications System (UMTS), the air interface suffers from a high-loss data rate. Thus, such systems involve some form of re-transmission protocol, such as radio link control (RLC) in the data link layer, or HARQ (Hybrid Automatic Repeat reQuest) functionality at the MAC (Medium Access Control) layer, to provide re-transmission functionality. Due to the need to perform retransmissions, and the constantly changing air interface conditions, the round trip time (RTT) for data packets (namely a time taken from a transmission of a packet to the receipt of an acknowledgement for the packet) is variable. As a result, such air interfaces are known to suffer from a high and variable communication latency.
A problem caused by the high latency of wireless communication systems is that, when a TCP packet is transmitted, a timer is started. If the sender of a TCP packet does not receive an acknowledgement for that packet before the timer reaches the determined RTO (retransmission time-out) value, the TCP packet will be re-transmitted. The RTO value is determined by measuring previous segment RTT values (a number of methods for determining RTO from previous measured segment RTT have been presented in [RFC793] and [V. Jacobsen, ‘Congestion avoidance and control, Computer communications review, 1988]). The TCP timer may therefore time-out, resulting in the re-transmission of the packet, whilst the RLC or HARQ is still in the process of trying to transmit the original instance of the packet over the air interface. As a result, the RLC may end up with two, and maybe more, instances of the same TCP packet to transmit across the air interface. Consequently, the same data packet may be effectively transmitted over the air interface twice or more. As will be appreciated by a skilled artisan, such duplication of data transmission is not only wasteful of air interface resources, but also further compounds the problem of the air interface suffering from a high latency.
Thus there exists a need for an improved method and apparatus for managing the transmission of data segments over an interface that substantially alleviates the above mentioned problems.